Display screen or portion thereof with a graphical user interface



The sole FIGURE is a front view of a display screen or portion thereofwith a graphical user interface showing our new design.

The outermost broken lines illustrate a device, or portion thereof, andedges of a display screen, or portion thereof, and form no part of theclaimed design. The remaining broken lines illustrating portions of thegraphical user interface, form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.